Kei Nishikori also booked his place in the quarter-finals after an epic encounter with fifth-seeded Canadian Milos Raonic which finished at 0226 in the morning local time - the joint latest finish in US Open history.

Nishikori, the 10th seed from Japan, looked on his way out as he trailed 2-1 heading into the fourth set but battled back to take the match 4-6 7-6 (7-4) 6-7 (6/8) 7-5 6-4 and set up a clash with Wawrinka.

The encounter lasted well over four hours but provided great entertainment for the sizeable crowd that stayed until the early hours to watch its completion.